LMV831: How to achieve this EMI-harded?

Brian Li

Expert 8885 points

Part Number: LMV831
Other Parts Discussed in Thread: LMV851

Hi all,

I noticed we have some devices like LMV831, LMV851 which are EMI-harded.

I saw the EMIRR is really higher, and I wonder how we achieve this EMI-harded.

Have we integrated an EMI filter in the device or which component in the chip made them EMI-harded?

Thanks,

Brian

over 1 year ago

+1 kai klaas69 over 1 year ago

Guru 140200 points

Hi Brian,

yes, there are small RC low pass filters added in the internal circuit. Of course, to not add unwanted phase shift the added RC filters must not be too heavy and must lie outside of the bandwidth of OPAmp. Because of this, they only work at frequencies beyond the unity gain bandwidth. See figure 42 of datasheet LMV831.

These internal EMI filters are helpful to enhance the immunity against cellphone radiation which otherwise could cause rectification effects. But because they do not work at lower frequencies, still following the usual design practises -filtering, shielding and grounding- is necessary. The internal EMI filtering must not be used as excuse to omit them. It's a nice to have, but no more.

Kai

0 Brian Li over 1 year ago in reply to kai klaas69

TI__Expert 8885 points

Hi Kai,

Thank you very much. It's crystal clear.

And I wonder if we have some guidance to choose opamps?

Thanks,

Brian

0 Pete%20Semig over 1 year ago in reply to Brian Li

TI__Mastermind 25795 points

Hello Brian,

We have a number of tools to help in op amp selection. Here are some links. If you need further help, don't hesitate to ask. Please be aware that you probably won't get a response until early next week due to Thanksgiving holiday.

Selguide

Quick search and Search by Circuit Function

3 considerations when selecting an op amp

Analog Engineer's Cookbook

AN-31 Amplifier Circuit Collection

Designing with General Purpose Op Amps

Amplifiers

Amplifiers forum

LMV831: How to achieve this EMI-harded?